1. Field of the Invention
This invention relates to an electric wire, which is enhanced on transmissibility of high-frequency current, especially to enlarge conductor skin effect in high-frequency current flow.
2. Description of the Related Art
When an alternating current flows as current I in an electrical conductive portion A, such as a metal, having uniform electrical conductivity σ and a frequency of the current is increased, the current does not flow in the center zone O of the electrical conductive portion A and the current flows concentratively in a surface zone B. The phenomenon is know as the conductor skin effect or the skin effect.
This phenomenon is caused by that an eddy current Ie to restrain a time response of a magnetic flux change by a circular magnetic field being generated in the conductive portion A by the current I and the eddy current Ie counterbalances the current I in the center zone of the conductive portion A and raises the current I in the surface zone B.
The current value is attenuated to 1/e at the skin depth δ being defined as a following formula:δ=(2/ωΞσ)1/2 ω=2πf                μ: magnetic permeability        σ: electrical conductivity        e: base of a natural logarithm, 2.71828.Thus, the current is decreasing in proportion to aparting from a surface.        
To increase a current value with the skin effect, a ratio of a surface area against a sectional area of the conductive portion A may be increased advantageously. A square electric wire having a conductive portion A′ with a square section as shown in FIG. 14 or a flat electric wire having a conductive portion A″ with a rectangular section as shown in FIG. 15 was proposed instead of a round electric wire having a conductive portion A with a round section as shown in FIG. 12.
Objects to be Solved
However, a square electric wire having a conductive portion A′ with a square section as shown in FIG. 14 or a flat electric wire having a conductive portion with a rectangular section as shown in FIG. 15 does not have enough current flow in a surface zone B by the skin effect. Especially, the transmissibility of current is being decreased in proportion to higher frequency.
To overcome the above drawback of prior art, one object of this invention is to provide an electric wire which is enhanced on transmissibility of high-frequency current, especially to enlarge conductor skin effect in high-frequency current flow.